Optical radiation, particularly laser light, is used extensively in communications, medicine, research, imaging, and in many other areas of technology. In such applications, laser radiation may be used directly or may be used as an intermediate pump source for purposes of promoting amplification or subsequent laser action. When an application's power requirements are small, on the order of several milliwatts more or less, and beam quality is not an overriding concern, laser diodes have been extensively employed because they are directly modulatable and of convenient size and acceptable beam quality. Where modest power is needed, on the order of a watt or so with superior beam quality, such as a diffraction-limited spot, optical fiber lasers with solid state pump sources have been used. For higher power applications where several watts may be needed, as in certain printing applications, use has been made of laser diode arrays as pump sources coupled to special fiber gain structures. For even higher power requirements, ten watts or more, high power laser diode arrays, whose cavities emit a few modes, may be coupled to such specialty gain fibers. However, care must be taken to assure efficient coupling power if maximum power benefit is to be achieved. Since single-mode cores are small, 10 .mu.m or less, and typical materials limit the size of fiber numerical apertures (NA), it is virtually impossible to efficiently couple multimode laser array energy directly into single-mode gain cores via endfire coupling techniques.
As mentioned above, high-power laser light can be obtained by combining the outputs from the emitting cavities of laser diode arrays. This typically is achieved by either focusing a plurality of laser beams onto a single point, or combining a plurality of laser beams into a focused beam pattern. The latter case is illustrated in U.S. Pat. No. 5,221,971 issued Jun. 22, 1993 to Allen et al. which discloses a printing method for combining a plurality of different sized laser beams into a beam pattern on a thermally sensitive medium for the purpose of producing hardcopy consisting of pixels whose size can be changed by area modulation to suit tonal content and detail while still maintaining a large number of gray levels per pixel. A beam pattern as disclosed by Allen et al. is illustrated in FIG. 5A herein.
In order to redirect a number of laser beams to form a laser pattern as shown in FIG. 5A, numerous separate discrete mirrors are utilized. For instance FIG. 3 shows four parallel laser beams 100, 102, 104 and 106 where beam 102 passes to the medium without reflection, beam 100 is reflected from a surface 109 of mirror 108, beam 106 is reflected from a surface 111 of mirror 110 and beam 104 is reflected from a surface 113 of mirror 112. In this case, a minimum of three mirrors positioned at various angles is required to direct the four laser beams into a parallel configuration. It is necessary to provide even more mirrors when it is desired to reflect a greater number of laser beams into a single pattern of parallel beams. The use of multiple mirrors becomes tedious and cumbersome, since each mirror must be perfectly aligned for proper operation. In other words, every mirror must be individually machined, installed and calibrated for use with a particular device. Precise changes in positioning of the mirrors is necessary yet difficult for proper beam alignment due to mechanical constraints.
It is an object of the current invention to provide a monolithic stationary multi-faceted mirror which is easy to machine, easy to install within tolerance without further calibration, and capable of reflecting two or more beams of light, preferably laser radiation, without detrimental feedback into the lasers from reflections of unwanted parts of the beams.
Other objects of the invention appear hereinafter and become apparent when reading the following detailed description in conjunction with the accompanying drawings.